The present invention relates to a method for calculating the diameter of a continuous-material reel on a roller, and to a reel-control system. The present invention also relates to a computer program and a computer program product.
Although the text below refers mainly to printing presses and their reel changers and control devices, the present invention is not limited thereto, but rather is directed to all types of web-processing machines with which the diameter of a continuous-material reel is to be determined. The present invention may be used, in particular, with printing presses such as newspaper presses, jobbing presses, gravure presses, printing presses for packaging or currency, and processing machines such as bagging machines, envelope machines, or packaging machines. The continuous material may be paper, cardboard, plastic, metal, rubber, or foil, etc.
The present invention may be used, in particular, to determine the diameter of continuous-material reels on reel carriers and/or reel changers. A reel changer typically includes at least two swivel arms that are swivelable about a swiveling axis, and on each of which a roller is mounted that is used to wind or unwind a material web. The swivel arms are typically free to swivel about the swiveling axis with the aid of an electric drive, so that a flying reel change may be carried out at full production speed. During processing, one of the rollers is connected with the machine via the material web, and the material web is either removed from the machine via the outfeed and wound onto the roller, or it is unwound from the roller and directed to the machine infeed. The roller is also driven by a drive, typically a center drive, a circumferential drive, or the like.
The diameter of the material web wound on the roller changes continually during the winding procedure and is determined by a reel-control system, e.g., based on the ratio of the winding speed to the web-conveyance speed. The web-conveyance speed is tapped at a reference axle, in particular a web-conveyance axle, with the reference axle defining a reference to the conveyance speed of the material web. The reference axle may also be a simulated or emulated axle (a “virtual” axle). The diameter of the reel is proportional to the ratio of the two known speeds. The reel-control system controls the winding process and the reel-changing process. During the reel-changing process, the swivel arm with the reel that is currently being used in production is swiveled away from the web-processing machine, and the swivel arm with the replacement reel is swiveled toward the web-processing machine. The swivel motion of the swivel arm affects the winding or unwinding speed, i.e., the rotational speed of the roller, since the roller must compensate for a lengthening or shortening of the length of the web by making an unwinding or winding motion. This compensation motion results in an effective winding or unwinding speed (rotational speed) that is no longer proportional to the diameter of the reel. The determination of the diameter during the swivel motion is therefore erroneous, with the error increasing as the web-conveyance speed slows, as the swivel speed increases, or the longer the swivel arm is.
With small reel diameters in particular, the swivel motion results in a large miscalculation. This is particularly problematic with unwind procedures, since, in this case, the reel change is typically carried out when the diameters are small. The relatively great error that results—for the reasons stated above—in the calculation of diameter is typically accompanied by a sufficient reserve of material on the roller. The material is therefore not utilized in an optimal manner.
To prevent the problems mentioned above, it is known to stop the calculation of diameter during a swivel motion. As a result, a current diameter value is not available for the period of time in which the swivel motion takes place, which is particularly disadvantageous when the reel diameter is small.
It is also known to specify a correction speed using a control system or entity that is higher-order than the reel control system. This is beset with several problems, since numerous quantities and/or parameters that are necessary in order to determine the correction speed must be transferred to the higher-order control system and/or must be determined by the control system.